Abstract: Method of logging a plurality of underground formations wherein a first and a second gamma ray emitting radioactive tracers with different energy levels are introduced into the formations. Logs are produced of the tracers as the traced fluids pass through the formations and thereafter the logs are analyzed to determined changes in effective permeabilities and sweep of the formations.

Abstract: An improved method for mobility control application in viscous oil reservoirs including (a) heating a lignosulfonate solution, prior to injection into an oil bearing formation, for a period of time sufficient to produce a more viscous lignosulfonate solution (e.g., 8% sodium lignosulfonate held at 375.degree. F. for 50 hours yielding a 86 cp fluid @ 84 sec.sup.-1 measured at room temperature), (b) cooling the resulting heat treated lignosulfonate fluid to a reservoir condition and (c) injecting this fluid into the formation. Fluids produced in this manner are useful as mobility buffers during a waterflood or a micellar flood process.

Abstract: A method of selective plugging of undesirable high permeability streaks and channels in oil-bearing reservoirs during high temperature (250.degree. F or higher) injection recovery processes such as steamflooding, underground combustion, flooding of a naturally occurring high-temperature reservoir or the like. Improved sweep efficiency can be effected by injecting a gel-forming solution consisting essentially of sodium or ammonium lignosulfonate and water or brine in the absence of other gelation promoters and then allowing the high temperatures of the underground formation to promote gelation. Optionally, a precooling water injection step can be used prior to placement of the gel-forming solution. This system has the advantage of gel times which are sufficiently long at temperatures in excess of 250.degree. F to permit placement of large volumes characteristic of commercial use. This method is particularly useful in selectively forming firm, strong gels in thief zones for steamflooding recovery operations.

Abstract: A method of selective plugging of undesirable high permeability streaks and channels in oil-bearing reservoirs during high temperature (250.degree. F. or higher) injection recovery processes such as steamflooding, underground combustion, flooding of a naturally occurring high-temperature reservoir or the like. Improved sweep efficiency can be effected by injecting a gel-forming solution consisting essentially of sodium or ammonium lignosulfonate and water or brine in the absence of other gelation promoters and then allowing the high temperatures of the underground formation to promote gelation. Optionally, a precooling water injection step can be used prior to placement of the gel-forming solution. This system has the advantage of gel times which are sufficiently long at temperatures in excess of 250.degree. F. to permit placement of large volumes characteristic of commercial use. This method is particularly useful in selectively forming firm, strong gels in thief zones for steamflooding recovery operations.